Radiative impact of the Hunga Tonga-Hunga Ha’apai stratospheric volcanic
plume: role of aerosols and water vapor in the southern tropical Indian
Ocean
Abstract
This study attempts to quantify the radiative impact over Reunion Island
(21°S, 55°E) in the southern tropical Indian Ocean of the aerosols and
water vapor injected in the stratosphere by the eruption on 15 January
2022 in the South Pacific of the Hunga Tonga-Hunga Ha’apai underwater
volcano. Ground-based lidar and satellite passive instruments are used
to parametrize a state-of-the-art radiative transfer model for the first
thirteen months after the volcano eruption. The descending rate of the
aerosol volcanic plume is -0.008 km day-1. At this rate, aerosols are
expected to be present in the stratosphere until the first half of 2025.
The overall aerosol and water vapor impact on the Earth’s radiation
budget for the whole period is positive (warming, +0.06 ± 0.45 W m-2)
and dominated by the aerosol impact. However, the decreasing rate with
time of the aerosol warming effect is larger than that of the water
vapor cooling effect, so that, in the long run, the impact on the
Earth’s radiation budget might reduce to quasi-neutral, or even become
slightly negative. At the Earth’s surface, aerosols are the main driver
and produce a negative (cooling, -0.91 ± 0.61 W m-2) radiative impact
with also a decreasing tendency with time. Heating/cooling rate profiles
show a clear vertical difference in the stratosphere between the aerosol
warming impact (17 to 25 km) and the water vapor cooling one (25 to 40
km).